The term bondage describes the practice of Physical restraining. Some are aroused from wetting their diapers, others like messing their diapers. The term is typically used by the cinematographer within the narrative framework of a pornographic film, and since the 1970s has become a leitmotif of the hardcore genre. Cartoon pornography includes, but is not limited to, hentai and parody renditions of famous cartoons and comics. Sub-genres can also be classified into the characteristics of the performers or the type of sexual activity on which it concentrates, and not necessarily on the market to which each sub-genre appeals. In S/M, the Sadist is usually the Top and the Masochist the Bottom, but these roles are frequently more complicated or jumbled . It is the most common form of sexual fetishism for otherwise non-sexual objects or body parts. In the gay pornography industry, which uses amateurs as well as professional actors, the term gay-for-pay refers to actors labeled or believed to be straight but who engage in same-sex sexual activities for money. These are often milf sex videos fake. Mutual masturbation, mutual manual stimulation of the genitals between partners, can be a substitute for sexual penetration. Group sex also occurs in populations of non-human animals such as bonobo apes and chimpanzees. Following World War II, during a period of social repression when governments actively persecuted homosexuals, women developed networks to socialize with and educate each other. At the end of the evening the female partners would randomly select keys from the bowl and leave with that key owner. Cartoon pornography depicts illustrated or animated fictional characters in erotic and sexual situations. Voyeur pornography may also include shots of topless women on topless beaches who are unaware of the cameras but may legally be photographed due to the public setting. Lolita pornography features women who are 18 years old or slightly older, who pretend to be underage teen girls. Among swinging couples, one of the two partners is often the driving force and the other is more passive-supportive of the addition of additional sex parties.